The invention relates in general to explosive and ignition trains for safety-and-arming devices and in particular to explosive and ignition trains for use with microelectromechanical systems (MEMS) safety-and-arming devices.
MEMS safety-and-arming devices currently being conceived and developed require detonating sources of a size such that conventional detonator fabrication techniques cannot be practically and economically employed. The detonating sources for state of the art MEMS safety-and-arming devices preferentially employ a maximum size of one cubic millimeter (mm). By comparison, the smallest mechanical detonator ever to enter widespread production has a total volume of nearly 34 cubic mm with a maximum dimension of 3.5 mm. The present invention, utilizing high density primary explosives, typically contains less than 10 mg of energetic material. In addition, the present invention represents the smallest practical size of a self-contained device which could possibly initiate a secondary explosive a short distance away, yet be fabricated and housed within a MEMS device.
The problem of low-energy energetic devices of about one cubic mm in size is a generic one. Energetic devices of this size are required for the vast majority of MEMS safety-and-arming devices that are contemplated for use in submunitions and other low-cost, high-volume applications that require a detonating output stimulus. While substantial attentions have been directed towards the fabrication of MEMS sensors, mechanical actuators and mechanisms in recent years, little or no effort has been directed towards the exploration of the energetics technologies to produce and control a detonation in such systems.
On the other hand, for systems in which relatively large electrical energies are available, interrupted electrical slapper detonator systems have been shown to be feasible initiators. The small bridge and flyer sizes needed to directly initiate explosives such as HNS-IV, and the ever-decreasing sizes of the requisite capacitors and switches, allow the slapper to be fabricated within a MEMS-device relatively easily. In addition, the acceptor explosive remains in the “macro” world and can be fabricated using well-known explosive powder-pressing techniques. MEMS units can then simply provide mechanical interruption between the flyer plate and acceptor explosive pellet, or in the most general case, an in-line explosive train whose arming energies are properly controlled (in accordance with Mil-Std-1316D) can also be utilized. Such electrically driven slapper devices, while sufficiently small to be fabricated within a MEMS device, require high electrical power and moderate electrical energies. Such slapper devices are relatively complex and expensive to fabricate making them inappropriate for low-energy, low-cost, high-volume MEMS applications, or MEMS applications where little or no onboard electrical energy is available.